Electrical measuring instrument



Jan. 4, 1944. F: J LlNGEL I 2,338,694

ELECTRICAL MEASURING INSTRUMENT Original Filed Aug. 11, 1941 MIVEIVTOP FREDERICK JTLINGEL,-

5 AITOP/VFVJ Patented Jan. 4, 1944 I 2,338,694 OFFICE ELECTRICAL MEASURING INSTRUMENT Frederick Joseph Lingel, Blulfton, Ohio, assignor to The Triplett Electrical Instrument Co., Bluffton, Ohio, a corporation of Ohio Original application August 11, 1941, Serial No. 406,336. Divided and this application March 9, 1942, Serial No. 433,959

6 Claims.

The present invention relates to electrical measuring devices and particularly to meters such as an ohm meter for determining the ratio between two currents or two voltages, etc.

This application is a division of my parent application, Serial No. 406,336, filed August 11. 1941.

The primary object of the present invention is to provide an improved measuring device for determining the ratio between two currents.

Another object is to provide an ohm meter in which the variations of the actuating electromotive force are utilized at the meter and do not affect the indications of the instrument.

Still another object is to provide a currentindicating ratio meter of a rugged character, and in which one or both of the measuring coils are stationary and the movable element or elements are constituted of magnetic vanes.

The general object of the invention is to provide an improved meter for giving an accurate direct reading of two or more current or voltage values in terms of their ratios, notwithstanding variations in the electromotive force which energizes the instrument.

Figure 1 shows one form of the improved ratio meter;

Figure 2 is a sectional view taken along the line 2-2 in Figure 1;

Figure 3 is a sectional 'view taken along the line 3-3 in Figure 2, and looking in the directio of the arrows;

Figure 4 is a sectional view taken along the line 4-4 in Figure 1.

The moving system of the usual type of DArsonval indicating electrical instrument is caused to deflect under the influence of a torque exerted thereon by current flowing through a coil suspended between the pole faces of a permanent magnet. The deflection is limited and the moving system comes to rest at a point where the restoring torque is equal and opposite to the deflecting torque. This restoring torque is usually applied to the moving system through a spiral torsion spring, which spring exerts a mechanical bias in direct proportion to the deflection. In many places where an electrical instrument of the indicating type could be used, the power supply is not; a constant voltage. Such application includes aircraft and automotive installation and many others where the source of power consists of a battery or generator. The voltage applied to the electrical circuit in such a system is subject to numerous influences tending to cause it to vary. For instance, both the batten and generator voltages are functions of the rate at which they are supplying power. The battery voltage is further affected by the amount it has been discharged. The generator voltage is also a function of its speed and would vary with the speed of its prime mover.

The above discussion as regards the introduction of errors by voltage fluctuation is also applicable to a moving van type instrument in which the torque is exerted on the moving system by the interaction of a magnetic field set up in a coil by a current flowing through the same, and an iron vane rotatably suspended in the field of the coil. In this case, the vane may be either permanently magnetized or not; In either case the net eifect of a voltage fluctuation is to cause the magnetic field to fluctuate and the reaction of the vane thereon to fluctuate. The fluctuating force exerted on the vane is opposed by a steady torsional force from the spiral spring and the moving system is, therefore, not at rest. Any measuring device, therefore, based on the voltage of a battery or generator balanced against the mechanical bias of a torsional spring will be in error by at least the same amount as the can be caused to recede from the cylinder I10 voltage.

The ratio meter shown in Figures 1 to 4 is contained within a case I64, the case being provided with a glass cover I at the top and closed at the bottom by a Plate I66. The case I64 contains a coil I61 wound on a webbed T-shaped form I68, of which the short leg extends in a vertical direction and is indicated at I69. There is a cylinder I10, of non-magnetic or magnetic metal, immediately surrounding the coil I61, this cylinder being secured to the closure plate I66 by screws I'II, positioned in the lugs I12. There is a magnetic vane I13 preferably magnetized, this vane being suspended in position from a rod I14 which is pivotally journalled as indicated at I15 in a U-shaped bearing member I16 which is secured to the top of the cylinder I10. The rod I 14 carries a pointer I11 and is adapted to swing over a dial I13.

Perpendicularly aligned with the horizontal axis of the coil I61, as seen in Figure 2, there is a coil I19, the effect of which, when energized, is to produce a magnetic field which passes through the cylinder I 10 and acts upon the magnetic vane I13. This coil is carried on a non-magnetic bobbin I which has a threaded bore extending longitudinally thereof. This bore receives a threaded rod It'l, the rod terminating at its left-hand end in a thumb nut I 82. This nut is provided with a shouldered portion I83 which bears against a nut I84, preferably of uniform thickness. Consequently by turning th thumb nut I82, for example in the counterclockwise direction looking from the left in Figure 3, the coil I19 and in this manner the intensity of the magnetic field impressed on the vane I13 is increased.

The bobbin I80 is also supported by a horizontally extending forked member I85 made of nonmagnetic material, the furcations of'which are preferably rectangular in shape and extend all the way through the bobbin. The legs of the forked member terminate at the left-hand end, as seen in Figure 3, in a shoe I88, which has an arcuate outer surface adapted to slide along the inner surface of the case I84. The shoe is threaded at its extreme left-hand end, as indicated at I81, to receive the nut I 84 which carries threads on its interior bore.

The case IE4 is provided with a horizontal slot I88, this slot extending over a limited angle and having a width loosely to accommodate a shouldered portion formed on the shoe I88, and also to accommodate the threaded portion I81 of the shoe. It is apparent that by loosening the nut I84 the shoe I 88 can be moved through an areaate path determined by the slot in the case I64, thus giving the coil I19 any desired angle of presentation to the vane I13. It has been pointed out that by turning the nut I82 in the counterclockwise direction the coil I19 can be caused to recede from the vane I13 so that any intensity of magnetic field produced by the coil I19 and any direction of the field with respect to the vane I13 may be obtained by manipulating the nuts I82 and I84.

In practice the coils I81 and I19 would be connected in any well-known and suitable manner so that the magnetic field generated by one of the coils, for example coil I81, would react on the magnetized vane I13 to move the pointer I11 over the dial in opposition to a restoring -force which may be exercised by the coil 119, also acting on the vane I13. The strength of this restoring force may be regulated by giving the coil I19 any desired cant or by moving the coil to any desired distance from the vane, in the manner described hereinbefore.

It will be understood that I desire to comprehend within my invention such modifications as come within the scope of the claims and the invention.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. An electrical measuring instrument for determining the ratio between two currents, said instrument comprising a pair of coils, means for mounting each of said coils, means for adjusting one of said coils for independent movement in either of two directions to vary the angular relationship of one coil with respect to the other, a magnetic vane contained in one of said coils and responsive to the magnetic fields produced by both of said coils when energized respectively by said currents, said vane being carried on a rod which is'adapted to move, and a pointer seccured to said rod whereby when the coils are energized the pointer will take a position to indicate the ratio between said two currents.

2. An electrical measuring instrument for determining the ratio between two currents, said instrument comprising a pair of coils, means for mounting each of said coils, means for adjusting one of said coils for independent movement in either of two directions to vary the angular relationship of one coil with respect to the other, one of said coils being adapted to be moved along its axis so as to change its rectilinear distance with respect to the other coil, said movable-coil ing also adapted to move in an angular directi 11 whereby the intensity of the magnetic field o the movable coil, also the direction of the magn tic field are adapted to be changed, a magnetic vane contained in one of said coils and responsive to the magnetic fields produced by both of said coils when energized respectively by said termining the ratio between two currents, said currents, said vane being carried on a rod which is adapted to move, and a pointer secured to said rod whereby when the coils are energized the pointer will take a position to indicate the ratio between said two currents.

3. An electrical measuring instrument for determining the ratio between two currents, said instrument comprising a pair of coils, means for mounting each of said coils, means for adjusting one of said coils for independent movement in either of two directions to vary the angular relationship of one coil with respect to the other, oneof said coils being adapted to be moved along its axis so as to change its rectilinear distance with respect to the other coil, said movable coil being also adapted to move in an angular direction whereby the intensity of the magnetic field of the movable coil, also the direction of the magnetic field are adapted to be changed, a magnetic vane contained in the stationary coil and responsive to the magnetic fields produced by both of said coils when energized respectively by said currents, said yane being carried on a rod which is adapted to move, and a pointer secured to said rod whereby when the coils are energized the pointer will take a position to indicate the ratio between said two currents.

4. An electrical measuringinstrument for determining the ratio between two currents, said instrument comprising a pair of coils, the axes of which are positioned angularly with respect to one another, a magnetic vane contained in one of said coils and responsive to the magnetic fields produced by both of said coils when energi zed respectively by said currents, said coils being contained in a casing, means for mounting each of said coils, and means for adjusting one of said coils for independent movement in either of two directions, said means including an element which is accessible from the exterior of the casing.

5. An electrical measuring instrument for deinstrument comprising a pair of coils, the aXes of which are positioned angularly with respect to one another, a magnetic vane contained in one of said coils and responsive to the magnetic fields produced by both of said coils when energized respectively by said currents, said coils being contained in a casing, means mounting One of said .cc ls within the casing, and the other of said coils being mounted on a rod which extends through a slot in the casing, said rod being adapted to be moved circumferentially of the casing in order to vary the position of the coils with respect to one another.

6. An electrical measuring instrument for determining the ratio between two currents, said instrument comprising a pair of coils, the axes of which are positioned angularly with respect to one another, a magnetic vane contained in one of said coils and responsive to the magnetic fields produced by both of said coils when energized respectively by said currents, said coils being contained in a casing, one of said coils being mounted on a rod which extends through a slot in the casing, said rod being adapted to be moved circumferentially of the casing in order to vary the position of the coils with respect to one another, and means for locking said rod with respect to said casing after a predetermined circumferential movement of said rod has been made.

FREDERICK JOSEPH LINGEL. 

